There's a straight reading of her hiring; there's a political reading of her hiring, and then there's a conspiratorial reading of her hiring. My best guess is that the truth lies between the straight reading and the conspiratorial reading.
The straight reading: Patti Solis Doyle was hired because she fit what the campaign was looking for, she knows every Democrat in the universe, and can be trusted and discreet. As Mo Elleithee, a Clinton aide, said in a statement:
“Patti will be an asset and good addition to the Obama campaign. After nearly two decades in political life, she brings with her the ability to tap an extensive network that will be a huge asset to Senator Obama. As Senator Clinton has said, we’re all going to do our part to help elect Senator Obama as the next President of the United States,
The political reading: Obama is paving the way for Clinton to join the ticket.
The conspiratorial reading: there are a hundred political reasons to hire Patti Solis Doyle, but only one reason to put her in this specific job. It's not as if she's uniquely qualified for it, unless that unique qualification is the ability to disqualify Hillary Clinton.
My best reporting indicates that Obama has not figured out whom he wants on the ticket AND that he is NOT going to put Clinton on the ticket unless for some reason he has to. He has no incentive to deliberately send an F-U to Clinton world.
I suspect that the truth here is either
(a) that folks in the Obama campaign did not anticipate the reaction of some major Clinton donors and aides. After all, Hillaryland right now is beset by a case of recriminitus; After all, blaming Solis Doyle for the campaign's missteps is very much in right now; even neutral observers concede that her mistakes were major, and she has few defenders left. (Although: question: who made PSD her campaign manager?) Or..
(b) maybe that the Obama campaign did anticipate the reaction and yet could not be bothered to care what a few Clinton donors and former aides think. There are lots of Obama aides and advisers who don't think that the feelings of Hillary Clinton's inner circle are terribly important right now.